The present invention pertains generally to high-temperature resins and in particular to cyano-addition resins of oxyarylbisorthodinitriles.
It is known that certain bisorthodinitriles polymerize to form strong, high-temperature thermosetting resins. Examples of bisorthodinitriles suitable for producing these resins are disclosed in U.S. Pat. Nos. 4,056,560, 4,057,569, and 4,136,107 by James R. Griffith and Jacques G. O'Rear.
The structure of these resins is not completely known. For the following reasons, the principal mechanism of formation is theorized to be phthalocyanine nucleation. As the bisorthodinitriles polymerize, the color becomes progressively darker green in the manner similar to phthalocyanines. The polymerization is difficult to initiate and promote which indicates the formation of a large and complex nucleus such as the phthalocyanine nucleus by a large end group such as the phthalonitrile group.
These resins have properties that make them exceptionally suitable for structural resins. They have a maximum temperature stability in an oxygen-containing atmosphere of about 230.degree. C. which represents a significant improvement over epoxy resins. Water resistance as measured by the water-soak method is better than that of epoxy resins.
The structural strength of the resins is comparable to that of epoxy and polyimide resins. These resins have many advantages over polyimides due to the adsence of solvents, being less hydroscopic, not being thermoplastic with a low glass-transition temperature and having better water resistance. Thus these resins promise to be an important new class of structural resins.
Although the properties of these resins are excellent, many applications require resins which have a higher temperature stability, a greater resistance to oxidative or chemical attack, lower combustibility, and higher char formation and which are self-extinguishing.